24VDC Wind turbine - 6 Blade - Furling too much?

owen_aowen_a Posts: 20Registered Users ✭✭
Hi,

I have this wind turbine and I've noticed that the tail furls when a gust of wind comes. From what I know, furling is used to protect the Wind Turbine from damage due to high wind speeds. What I don't understand is that it's missing out on about 5-10 seconds of a powerful gust that could potentially be used to charge my battery up. However, instead, the tail furls quite easily. I could "disable" it by tightening it up and lodging something around the section where it can move freely where it is attached. What do you think? Is this furling meant to happen? Or is it only meant to happen in higher winds? The tail is held in place so the turbine doesn't face where the gust is coming from, until it falls back into place, but even then, it can move out of place and miss out on that wind again. I'll see if I can record a video and show you more clearly.

EDIT: It happens at about 1:36 onwards, the tail furls, so the turbine isn't able to direct it self into the gust.

Thanks,
Owen.

Comments

  • BB.BB. Posts: 27,681Super Moderators admin
    Looks like the turbine is too close to the ground / to close to nearby obstructions (house/trees/etc.). Lots of changes in wind direction and even no wind--while the clouds overhead are moving at a steady pace. I wonder if the furling we saw was actually caused by a dramatic shift in wind direction.

    In itself, losing 5-10 seconds of production out of 2 minutes of operation is not the end of the world (5% loss of production). The turbulent airflow is probably costing you a lot more production.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • owen_aowen_a Posts: 20Registered Users ✭✭
    Ah I see. So turbulence is to blame due to it being too near houses, trees, etc?
  • BB.BB. Posts: 27,681Super Moderators admin
    Just a guess... If you are interested, try flying a kite. See how high it has to fly before it enters stable airflow. That is where the wind turbine wants to fly.

    There is very little "useful" energy in turbulent airflow.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Posts: 3,874Solar Expert ✭✭✭✭
    And it is much easier to sleep inside of the turbulent flow with that thing running outside in the stable flow.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • owen_aowen_a Posts: 20Registered Users ✭✭
    Is there any modifications I can do to increase production? I thought about tightening the locking nut so it cannot furl. My first AC wind turbine had a tail that was screwed onto the actual housing thus didn't have any furling mechanism. That pointed in the wind all day long. The problem with that is that it was 12V AC and required a very strong wind (needed to be rotated very fast) to generate any usable voltage. It pumped out amps though!
  • BB.BB. Posts: 27,681Super Moderators admin
    Any mechanical changes you make up the risk of failure (blades flying off turbine, nacel falling to ground, tower collapsing).

    In the end, you are seeing why we really do not suggest installing a wind turbine unless you are able to fly it in clean air flow and away from houses/people--They fail too often at the best of times. And usually fail to generate anywhere near the expected/advertised amount of power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • owen_aowen_a Posts: 20Registered Users ✭✭
    Hi,

    I'd thought I'd revive this thread since I came up with an idea since the wind is up again and my turbines furling like no tomorrow.

    My first wind turbine had the centre of the tail cut out so it was holo, so it only had a "border" in a sense acting as the tail and I believe this worked great in my current situation since I'm surrounded by houses / trees. 

    This is the only image I could find of the turbine and tail so you can see what I'm on about;



    I was wondering, with my current wind turbine as you can see in the video above, I could cut out the centre part of the tail so it would reduce the amount of wind striking the tail (so it could flow through it instead) thus keeping the turbine in the direction of the wind without the disturbed air flow pushing the tail around.

    Here is a very crude sketch I did in paint. The red line shows what I'd cut so the centre part is removed (I'm no artist :smile: )



    What are your thoughts?
  • BB.BB. Posts: 27,681Super Moderators admin
    Many folks have had problems with turbines not pointing into the wind with small tails (not enough surface area/moment arm to point turbine into the wind).

    Remember your theory is that the sideway gust is being "dumped" via the smaller surface area of the tail. But, that change in direction (or the gust) is also what the turbine blades are "seeing" too. The wind is not going "sideways" through the tail while flowing through the blades "straight on". Both the tail and the blades are in sideways airflow and the blades cannot extract any energy from that flow.

    Did you ever try flying a kit in that weather to see how high the turbine would have to fly to be in non-turbulent air?

    Have you measured the monthly power harvest of your turbine to see how much power it does generate?

    When you do not have high winds (i.e., destructive to the turbine) in the forecast, perhaps you would want to try to adjust/tighten/fix the turbine tail and try a day with it "fixed" to see if you do generate significantly more power, or not.

    Normally, I would suggest that you compare wind turbines against solar panels... But if you are somewhere around Basildon UK, you, on average, do not have a lot of sun:
    http://pvwatts.nrel.gov/pvwatts.php
    MonthSolar Radiation
    ( kWh / m2 / day )
    January1.45
    February1.90
    March2.55
    April3.97
    May4.57
    June4.34
    July4.60
    August4.50
    September3.56
    October2.64
    November1.62
    December0.97
    Annual3.06
    Let's guess that you get a 100 kWH per month or ~3.3 kWH per day during winter from your turbine (that, I think, is way over what you actually harvest), and want to replace energy during December:
    • 3,300 WH per day * 1/0.52 typical off grid system eff * 1/0.97 hours of sun (Dec) = 6,542 Watt array
    That is a large array for such small amount of output... However, I really do wonder how much power your wind turbine outputs in a day/month. From watching your original video and how little time it spends actually turning (clouds are moving consistently, but turbine in stopped in turbulent flow), you are probably only capturing 5% or or even much less of its capabilities (in strong/steady wind).
    • 300 Watts * 0.05 actual harvest eff * 24 hours per day = 360 Watt*Hours per day (my guess from 1/2 a world away)
    • 360 WH per day * 1/0.52 off grid solar eff * 1/0.97 hours of sun for December = 714 Watt array
    For a 714 Watt array, 6 months of the year ("summer"), 3.56 hours of sun minimum:
    • 714 Watt array * 0.52 off grid system eff * 3.56 hours of sun (September average) = 1,322 WH per day (or better for ~6 months a year)
    Or over 3x what, I guess, your best month average for your wind turbine would be.

    Just to give some ideas about how difficult it is to generate energy from the wind:

    http://forum.solar-electric.com/discussion/5131/skystream-20-000-lawn-ornament (some useful links in first page of discussion)
    http://forum.solar-electric.com/discussion/340203/a-1-8kw-wind-turbine-and-a-1kw-solar-panel-what-could-that-run (actual numbers from a "well working" 3.7 meter ~2,000 Watt turbine vs your ~1.1 meter 300 Watt turbine).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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